Optimal pressure for mimicking clinical breath holding inspiratory CT in the deceased for VPMCT

Introduction

Ventilated PMCT (VPMCT) has been reported to provide better quality of pulmonary structures in PMCT in adults and children. However, there are no consensus regarding optimal inflation pressure, and the practical use of VPMCT is still limited by cost of ventilation equipment. Here, we describe a simple and cost-efficient inflation-device for VPMCT and investigate optimal inflation pressure.

Aim

To elucidate the effect of different ventilation pressures on total lung volume and the volume of ground glass opacities (GGO), air-filled tissue, consolidations, and bronchi in VPMCT.

Materials and method

A precise inflation device was assembled using standard components: a back-pressure regulator, a water manometer and silicone tubing. Each case had PMCT performed at 0, 10, 20, 30 and 40 cmH₂O pressure. Volumes were measured using stereology.

Results

14 cases were enrolled in the study. The total lung volume increased significantly by 3612 mL (median) from 0 to 30 cmH₂O (p = 0.001). The volume of consolidations was significantly reduced by 455.86 mL (median) between 0 and 30 cmH₂O (p = 0.001). A significant reduction of GGO-volume of 133 mL (median) was observed at the pressure interval 30–40 cmH₂O (p = 0.031), but not at lower pressures.

Conclusion

The constructed inflation device allowed precise and reproducible inflation of the lungs in deceased humans. We found a maximum effect of inflation at 30 cmH₂O. At further inflation pressure, only the volume of GGOs decreased , but the effect was minor. For mimicking an in vivo breath-hold scan in PMCT we recommend inflation pressure of 30 cmH₂O.